1. Field of the Invention
The invention relates to the field of the electrical power supply of light sources, more precisely of light-emitting diodes, or LEDs. In particular, the invention relates to a system and method for controlling the electrical power supply of a plurality of light sources, arranged into several groups. Each group is powered by a series connection of a step-up voltage converter, for example of the boost type, and of a step-down voltage converter, for example of the buck type, the step-up converters of all the groups operating as a multiphase step-up voltage converter. The invention also relates to a lighting system for an automobile vehicle
2. Description of the Related Art
A light-emitting diode, or LED, is an electronic component capable of emitting light when it has an electrical current flowing through it. The light intensity emitted by a LED is in general dependent on the intensity of the electrical current flowing through it. In the automobile field, LED technology is increasingly being used in various lighting and signaling solutions.
A control circuit is used to control the current through an assembly or group of LEDs. The circuit defines the current flowing through a branch connected as a load and comprising the group of LEDs connected in series. A known solution is to use separate control circuits powering separate groups of LEDs, each group fulfilling a separate lighting function of an automobile vehicle. Amongst others, such functions comprise the high and low beam lights or the side lights. A known solution is to power each function independently from the other functions by a dedicated control circuit.
A dedicated control circuit comprises for example a step-up (boost) converter followed in series by a step-down (buck) converter. In such a case, the measurement of the input current of a dedicated control circuit gives, at any time, an indication relating to the output power required by the function in question. This indication is for example used by diagnostic means for the operation of the lighting functions of the automobile vehicle.
It is becoming more and more common to use a multiphase step-up voltage converter common to each of the lighting functions, followed in series by buck converters dedicated by function. A multiphase converter is obtained by connecting at the output several voltage step-up converters having a common control. The individual step-up converters acting as phases of the multiphase converter contribute in a combined manner to obtaining a common output voltage. The current consumed by each of the lighting functions is, in this case, supplied by a common control circuit. The measurement of the input current for each of the phases of the multiphase step-up converter is no longer necessarily representative of the output power required by each of the functions. A diagnostic system using the indication supplied by the input currents in order to deduce the state of operation of the respective lighting functions is no longer therefore capable of supplying reliable diagnostic indications. Indeed, the detection of false positives and/or false negatives may be the consequence of the use of the intensity of the input current of each individual step-up converter, which has now become an unsuitable quantity.